CVE-2020-36406: uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS

Q: How do I fix CVE-2020-36406?

uwebsockets: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2020-36406 being exploited?

CVE-2020-36406 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-36406 affect?

CVE-2020-36406 affects uwebsockets. Severity is high (CVSS 8.8). uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS::TopicTree::unsubscribeAll). NOTE: the vendor's position is that this is "a minor issue or not even an issue at all" because the

Q: How urgent is CVE-2020-36406?

Priority 54/100. High severity; Public exploit reference

This month

HIGH 8.8DOWNGRADE

CVE-2020-36406 is a high-severity flaw (CVSS 8.8) affecting uwebsockets. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS::TopicTree::unsubscribeAll). NOTE: the vendor's position is that this is "a minor issue or not even an issue at all" because the developer of an application (that uses uWebSockets) should not be allowing the large number of triggered topics to accumulate

Why this priority

High severity
Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.5% (top 25%)
CISA exploited list	No
Weakness	CWE-787
Published	2021-07-01
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: uwebsockets project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-07-01 03:15 UTCPublished CVE record published
2026-06-17 03:15 UTCUpdated Record last modified

uwebsockets project uwebsockets DOWNGRADE

Affected: 18.11.0 · 18.12.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 18.11.0

1. Check installed version

npm ls uwebsockets

2. No fixed release: DOWNGRADE to a release before 18.11.0

npm view uwebsockets versions npm install uwebsockets@"<18.11.0"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-36406?

uwebsockets: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-36406 being exploited?

CVE-2020-36406 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-36406 affect?

CVE-2020-36406 affects uwebsockets. Severity is high (CVSS 8.8). uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS::TopicTree::unsubscribeAll). NOTE: the vendor's position is that this is "a minor issue or not even an issue at all" because the

How urgent is CVE-2020-36406?

Priority 54/100. High severity; Public exploit reference

References

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